1. Field of the Invention
The present invention relates to a transmission characteristics analyzing device which analyzes the transmission characteristics of a communication network, and a program which causes a computer to operate as the transmission characteristics analyzing device.
2. Description of Related Art
Recently, an information transmission technology for using, as a communication network, a power line, such as a power line which is wired indoors, has been developed, and actual use of the information transmission technology has been considered. Power lines are dedicated networks for power supply. Therefore, signal reflection or impedance mismatch sometimes degrades the transmission characteristics when a signal of a high frequency is transmitted by power distribution networks.
It is therefore necessary to analyze the transmission characteristics of a power line to point out locations where the transmission performance is degraded in the distribution power system and to study how to cope with the problem. There has been provided a transmission characteristics analyzing method (for example, refer to patent reference 1) using an equivalent circuit with connections of four-terminal circuit elements between an element for a transmitting point and an element for a receiving point to calculate the transmission characteristics of the network.
[Patent reference 1] JP, 2003-44532, A
Patent reference 1 is intended for a case where a lamp line in which only circuits which are equivalent when viewed from both their output and input sides (referred to as components with symmetric I/O from here on), such as cables, branch points, and terminals, exist as circuit elements is used as a communication network. Thus, the related art transmission characteristics analyzing method is based on the premise that only components with symmetric I/O exist. Therefore, the directions in which signals flow in the communication network are not taken into consideration, and, when a component with asymmetric I/O exists in the communication network, it is impossible to calculate the transmission characteristics of the communication network using the related art transmission characteristics analyzing method.
For example, when using a power line as a communication network, power always flows from a power source to a power load, but a signal changes its direction which it flows according to the transmitting and receiving points thereof. Unlike a communications dedicated liner a power line may include a component with asymmetric I/O, such as a transformer. A four-terminal circuit which is equivalent to such a component with asymmetric I/O differs according to the direction in which a signal flows through the four-terminal circuit. For this reason, when calculating the transmission characteristics of a power line, it is necessary to consider the direction in which the signal flows from its transmitting point to its receiving point, and to generate and combine four-terminal circuits according to the direction in which the signal flows.